1
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Picco G, Rao Y, Al Saedi A, Lee Y, Vieira SF, Bhosle S, May K, Herranz-Ors C, Walker SJ, Shenje R, Dincer C, Gibson F, Banerjee R, Hewitson Z, Werner T, Cottom JE, Peng Y, Deng N, Landis P, Conticelli D, McCarten K, Bush J, Sharma M, Lightfoot H, House D, Milford E, Grant EK, Glogowski MP, Wagner CD, Bantscheff M, Rutkowska-Klute A, Network Uk Group CM, Zappacosta F, Pettinger J, Barthorpe S, Eberl HC, Jones BT, Schneck JL, Murphy DJ, Voest EE, Taygerly JP, DeMartino MP, Coelho MA, Houseley J, Sharma G, Schwartz BJ, Garnett MJ. Novel WRN Helicase Inhibitors Selectively Target Microsatellite Unstable Cancer Cells. Cancer Discov 2024:742950. [PMID: 38587317 DOI: 10.1158/2159-8290.cd-24-0052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Revised: 03/26/2024] [Accepted: 04/05/2024] [Indexed: 04/09/2024]
Abstract
Microsatellite-unstable (MSI) cancers require WRN helicase to resolve replication stress due to expanded DNA (TA)n-dinucleotide repeats. WRN is a promising synthetic lethal target for MSI tumours, and WRN inhibitors are in development. Here, we used CRISPR-Cas9 base editing to map WRN residues critical for MSI cells, validating the helicase domain as the primary drug target. Fragment-based screening led to the development of potent and highly selective WRN helicase covalent inhibitors. These compounds selectively suppressed MSI model growth In vitro and In vivo by mimicking WRN loss, inducing DNA double-strand breaks at expanded TA-repeats and DNA damage. Assessment of biomarkers in preclinical models linked TA-repeat expansions and mismatch repair (MMR) alterations to compound activity. Efficacy was confirmed in immunotherapy-resistant organoids and patient-derived xenograft (PDX) models. The discovery of potent, selective covalent WRN inhibitors provides proof of concept for synthetic-lethal targeting of WRN in MSI cancer and tools to dissect WRN biology.
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Affiliation(s)
| | - Yanhua Rao
- GSK, Upper Providence, PA, US 19426, United States
| | | | - Yang Lee
- GSK, Upper Providence, PA, US 19426, United States
| | | | | | - Kieron May
- Babraham Institute, Cambridge, United Kingdom
| | | | | | | | - Cansu Dincer
- Wellcome Sanger Institute, Cambridge, United Kingdom
| | - Freddy Gibson
- Wellcome Sanger Institute, Cambridge, United Kingdom
| | | | - Zoe Hewitson
- Wellcome Sanger Institute, Cambridge, United Kingdom
| | | | - Joshua E Cottom
- GlaxoSmithKline (United States), Upper Providence, PA, United States
| | - Yang Peng
- The University of Texas MD Anderson Cancer Center, Houston, TEXAS, United States
| | | | | | - Daniela Conticelli
- University of Torino, Candiolo Cancer Institute - FPO,IRCCS, Candiolo, TO, Italy
| | | | | | - Mamta Sharma
- Wellcome Sanger Institute, Cambridge, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | - Syd Barthorpe
- Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | | | | | | | | | - Emile E Voest
- Netherlands Cancer Institute, Amsterdam, Netherlands
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2
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Borrelli W, Mei KJ, Park SJ, Schwartz BJ. Partial Molar Solvation Volume of the Hydrated Electron Simulated Via DFT. J Phys Chem B 2024; 128:2425-2431. [PMID: 38422045 PMCID: PMC10945486 DOI: 10.1021/acs.jpcb.3c05091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 02/03/2024] [Accepted: 02/14/2024] [Indexed: 03/02/2024]
Abstract
Different simulation models of the hydrated electron produce different solvation structures, but it has been challenging to determine which simulated solvation structure, if any, is the most comparable to experiment. In a recent work, Neupane et al. [J. Phys. Chem. B 2023, 127, 5941-5947] showed using Kirkwood-Buff theory that the partial molar volume of the hydrated electron, which is known experimentally, can be readily computed from an integral over the simulated electron-water radial distribution function. This provides a sensitive way to directly compare the hydration structure of different simulation models of the hydrated electron with experiment. Here, we compute the partial molar volume of an ab-initio-simulated hydrated electron model based on density-functional theory (DFT) with a hybrid functional at different simulated system sizes. We find that the partial molar volume of the DFT-simulated hydrated electron is not converged with respect to the system size for simulations with up to 128 waters. We show that even at the largest simulation sizes, the partial molar volume of DFT-simulated hydrated electrons is underestimated by a factor of 2 with respect to experiment, and at the standard 64-water size commonly used in the literature, DFT-based simulations underestimate the experimental solvation volume by a factor of ∼3.5. An extrapolation to larger box sizes does predict the experimental partial molar volume correctly; however, larger system sizes than those explored here are currently intractable without the use of machine-learned potentials. These results bring into question what aspects of the predicted hydrated electron radial distribution function, as calculated by DFT-based simulations with the PBEh-D3 functional, deviate from the true solvation structure.
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Affiliation(s)
| | | | - Sanghyun J. Park
- Department of Chemistry and
Biochemistry, University of California,
Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J. Schwartz
- Department of Chemistry and
Biochemistry, University of California,
Los Angeles, Los Angeles, California 90095-1569, United States
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3
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Mei K, Borrelli WR, Vong A, Schwartz BJ. Using Machine Learning to Understand the Causes of Quantum Decoherence in Solution-Phase Bond-Breaking Reactions. J Phys Chem Lett 2024; 15:903-911. [PMID: 38241152 PMCID: PMC10839908 DOI: 10.1021/acs.jpclett.3c03474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 01/11/2024] [Accepted: 01/16/2024] [Indexed: 01/21/2024]
Abstract
Decoherence is a fundamental phenomenon that occurs when an entangled quantum state interacts with its environment, leading to collapse of the wave function. The inevitability of decoherence provides one of the most intrinsic limits of quantum computing. However, there has been little study of the precise chemical motions from the environment that cause decoherence. Here, we use quantum molecular dynamics simulations to explore the photodissociation of Na2+ in liquid Ar, in which solvent fluctuations induce decoherence and thus determine the products of chemical bond breaking. We use machine learning to characterize the solute-solvent environment as a high-dimensional feature space that allows us to predict when and onto which photofragment the bonding electron will localize. We find that reaching a requisite photofragment separation and experiencing out-of-phase solvent collisions underlie decoherence during chemical bond breaking. Our work highlights the utility of machine learning for interpreting complex solution-phase chemical processes as well as identifies the molecular underpinnings of decoherence.
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Affiliation(s)
- Kenneth
J. Mei
- Department of Chemistry &
Biochemistry, University of California,
Los Angeles, Los Angeles, California 90095-1569, United States
| | - William R. Borrelli
- Department of Chemistry &
Biochemistry, University of California,
Los Angeles, Los Angeles, California 90095-1569, United States
| | - Andy Vong
- Department of Chemistry &
Biochemistry, University of California,
Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J. Schwartz
- Department of Chemistry &
Biochemistry, University of California,
Los Angeles, Los Angeles, California 90095-1569, United States
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4
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Wu EC, Schwartz BJ. Does the Traditional Band Picture Describe the Electronic Structure of Doped Conjugated Polymers? TD-DFT and Natural Transition Orbital Study of Doped P3HT. J Chem Theory Comput 2023; 19:6761-6769. [PMID: 37769199 DOI: 10.1021/acs.jctc.3c00743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Polarons and bipolarons are created when one or two electrons are removed from the π-system of a p-type conjugated polymer, respectively. In the traditional band picture, the creation of a polaron causes two electronic energy levels to move into the band gap. The removal of a second electron to form a bipolaron causes the two intragap states to move further into the gap. Several groups, however, who looked at the energies of the Kohn-Sham orbitals from DFT calculations, have recently argued that the traditional band picture is incorrect for explaining the spectroscopy of doped conjugated polymers. Instead, the DFT calculations suggest that polaron creation causes only one unoccupied state to move into the band gap near the valence band edge while half-filled state in the valence band and the conduction band bend downward in energy. To understand the discrepancy, we performed TD-DFT calculations of polarons and bipolarons on poly(3-hexylthiophene) (P3HT). Not only do the TD-DFT-calculated absorption spectra match the experimental absorption spectra, but an analysis using natural transitional orbitals (NTOs), which provides an approximate one-electron picture from the many-electron TD-DFT results, supports the traditional band picture. Our TD-DFT/NTO analysis indicates that the traditional band picture also works for bipolarons, a system for which DFT calculations were unable to determine the electronic structure.
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Affiliation(s)
- Eric C Wu
- Department of Chemistry and Biochemistry University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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5
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Darzi ER, Stanfield DA, McDermott L, Kelleghan AV, Schwartz BJ, Garg NK. Facile synthesis of 2-aza-9,10-diphenylanthracene and the effect of precise nitrogen atom incorporation on OLED emitters performance. Mater Adv 2023; 4:3351-3355. [PMID: 37588776 PMCID: PMC10388396 DOI: 10.1039/d3ma00280b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 07/12/2023] [Indexed: 08/18/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are important compounds in materials chemistry, particularly for optoelectronic applications. One strategy for tuning PAH properties involves the net exchange of carbon atoms for heteroatoms, such as nitrogen. We report a comparative study of the well-known fluorophore 9,10-diphenylanthracene with an aza analog. The latter compound is accessed using a short sequence involving the use of two strained cyclic alkynes, benzyne and a 3,4-piperidyne, in Diels-Alder cycloaddition sequences. Comparative studies of 9,10-diphenylanthracene and the aza-analog show how the addition of a single nitrogen atom impacts electrochemical and optical properties. Organic light-emitting diode (OLED) devices were prepared using both compounds, which showed that nitrogen substitution leads to an unexpected red shift in electroluminescence, likely due to exciplex formation between the active layer and the 4,4'-N,N'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) hole-transport layer. These studies highlight a unique approach to accessing heteroatom-containing PAHs, while underscoring the impact of heteroatoms on OLED device performance.
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Affiliation(s)
- Evan R Darzi
- Department of Chemistry and Biochemistry, University of California at Los Angeles Los Angeles California 90095 USA
| | - Dane A Stanfield
- Department of Chemistry and Biochemistry, University of California at Los Angeles Los Angeles California 90095 USA
| | - Luca McDermott
- Department of Chemistry and Biochemistry, University of California at Los Angeles Los Angeles California 90095 USA
| | - Andrew V Kelleghan
- Department of Chemistry and Biochemistry, University of California at Los Angeles Los Angeles California 90095 USA
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California at Los Angeles Los Angeles California 90095 USA
| | - Neil K Garg
- Department of Chemistry and Biochemistry, University of California at Los Angeles Los Angeles California 90095 USA
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6
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Park SJ, Schwartz BJ. How Ions Break Local Symmetry: Simulations of Polarized Transient Hole Burning for Different Models of the Hydrated Electron in Contact Pairs with Na . J Phys Chem Lett 2023; 14:3014-3022. [PMID: 36943261 DOI: 10.1021/acs.jpclett.3c00220] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The hydrated electron (eaq-) is known via polarized transient hole-burning (pTHB) experiments to have a homogeneously broadened absorption spectrum. Here, we explore via quantum simulation how the pTHB spectroscopy of different eaq- models changes in the presence of electrolytes. The idea is that cation-eaq- pairing can break the local symmetry and, thus, induce persistent inhomogeneity. We find that a "hard" cavity model shows a modest increase in the pTHB recovery time in the presence of salt, while a "soft" cavity model remains homogeneously broadened independent of the salt concentration. We also explore the orientational anisotropy of a fully ab initio density functional theory-based model of the eaq-, which is strongly inhomogeneously broadened without salt and which becomes significantly more inhomogeneously broadened in the presence of salt. The results provide a direct prediction for experiments that can distinguish between different models and, thus, help pin down the hydration structure and dynamics of the eaq-.
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Affiliation(s)
- Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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7
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Park SJ, Narvaez WA, Schwartz BJ. Ab Initio Studies of Hydrated Electron/Cation Contact Pairs: Hydrated Electrons Simulated with Density Functional Theory Are Too Kosmotropic. J Phys Chem Lett 2023; 14:559-566. [PMID: 36630724 DOI: 10.1021/acs.jpclett.2c03705] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
We have performed the first DFT-based ab initio MD simulations of a hydrated electron (eaq-) in the presence of Na+, a system chosen because ion-pairing behavior in water depends sensitively on the local hydration structure. Experiments show that eaq-'s interact weakly with Na+; the eaq-'s spectrum blue shifts by only a few tens of meV upon ion pairing without changing shape. We find that the spectrum of the DFT-simulated eaq- red shifts and changes shape upon interaction with Na+, in contrast with experiment. We show that this is because the hydration structure of the DFT-simulated eaq- is too ordered or kosmotropic. Conversely, simulations that produce eaq-'s with a less ordered or chaotropic hydration structure form weaker ion pairs with Na+, yielding predicted spectral blue shifts in better agreement with experiment. Thus, ab initio simulations based on hybrid GGA DFT functionals fail to produce the correct solvation structure for the hydrated electron.
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Affiliation(s)
- Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Wilberth A Narvaez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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8
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Narvaez WA, Park SJ, Schwartz BJ. Competitive Ion Pairing and the Role of Anions in the Behavior of Hydrated Electrons in Electrolytes. J Phys Chem B 2022; 126:7701-7708. [PMID: 36166380 DOI: 10.1021/acs.jpcb.2c04463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Experiments have shown that in the presence of electrolytes, the hydrated electron's absorption spectrum experiences a blue shift whose magnitude depends on both the salt concentration and chemical identity. Previous computer simulations have suggested that the spectral blue shift results from the formation of (cation, electron) contact pairs and that the concentration dependence arises because the number of cations simultaneously paired with the electron increases with increasing concentration. In this work, we perform new simulations to build an atomistic picture that explains the effect of salt identity on the observed hydrated electron spectral shifts. We simulate hydrated electrons in the presence of both monovalent (Na+) and divalent (Ca2+) cations paired with both Cl- and a spherical species representing ClO4- anions. Our simulations reproduce the experimental observations that divalent ions produce larger blue shifts of the hydrated electron's spectrum than monovalent ions with the same anion and that perchlorate salts show enhanced blue shifts compared to chloride salts with the same cation. We find that these observations can be explained by competitive ion pairing. With small kosmotropic cations such as Na+ and Ca2+, aqueous chloride salts tend to form (cation, anion) contact pairs, whereas there is little ion pairing between these cations and chaotropic perchlorate anions. Hydrated electrons also strongly interact with these cations, but if the cations are also paired with anions, this affects the free energy of the electron-cation interaction. With chloride salts, hydrated electrons end up in complexes containing multiple cations plus a few anions as well as the electron. Repulsive interactions between the electron and the nearby Cl- anions reduce the cation-induced spectral blue shift of the hydrated electron. With perchlorate salts, hydrated electrons pair with multiple cations without any associated anions, leading to the largest possible cation-induced spectral blue shift. We also see that the reason multivalent cations produce larger spectral blue shifts than monovalent cations is because hydrated electrons are able to simultaneously pair with a larger number of multivalent cations due to a larger free energy of interaction. Overall, the interaction of hydrated electrons with electrolytes fits well with the Hofmeister series, where the electron behaves as an anion that is slightly more able to break water's H-bond structure than chloride.
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Affiliation(s)
- Wilberth A Narvaez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
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9
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Narvaez WA, Wu EC, Park SJ, Gomez M, Schwartz BJ. Trap-Seeking or Trap-Digging? Photoinjection of Hydrated Electrons into Aqueous NaCl Solutions. J Phys Chem Lett 2022; 13:8653-8659. [PMID: 36083839 DOI: 10.1021/acs.jpclett.2c02243] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
It is well-known that when excess electrons are injected into an aqueous solution, they localize and solvate in ∼1 ps. Still debated is whether localization occurs via "trap-digging", in which the electron carves out a suitable localization site, or by "trap-seeking", where the electron prefers to localize at pre-existing low-energy trap sites in solution. To distinguish between these two possible mechanisms, we study the localization dynamics of excess electrons in aqueous NaCl solutions using both ultrafast spectroscopy and mixed quantum-classical molecular dynamics simulations. By introducing pre-existing traps in the form of Na+ ions, we can use the cation-induced blue-shift of the hydrated electron's absorption spectrum to directly monitor the site of electron localization. Our experimental and computational results show that the electron prefers to localize directly at the sites of Na+ traps; the presence of concentrated electrolytes otherwise has little impact on the way trap-seeking hydrated electrons relax following injection.
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Affiliation(s)
- Wilberth A Narvaez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Eric C Wu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Mariah Gomez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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10
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Abstract
In solution-phase chemistry, the solvent is often considered to be merely a medium that allows reacting solutes to encounter each other. In this work, however, we show that moderate locally specific solute-solvent interactions can affect not only the nature of the solute but also the types of reactive chemistry. We use quantum simulation methods to explore how solvent participation in solute chemical identity alters reactions involving the breaking of chemical bonds. In particular, we explore the photoexcitation dynamics of Na2+ dissolved in liquid tetrahydrofuran. In the gas phase, excitation of Na2+ directly leads to dissociation, but in solution, photoexcitation leads to an isomerization reaction involving rearrangement of the first-shell solvent molecules; this isomerization must go to completion before the solute can dissociate. Despite the complexity, the solution-phase reaction dynamics can be captured by a two-dimensional energy surface where one dimension involves only the isomerization of the first-shell solvent molecules.
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Affiliation(s)
- Andy Vong
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Kenneth J Mei
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Devon R Widmer
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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11
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Abstract
Solvent effects are important for understanding solution-phase chemical reactions. Surprisingly, very few studies have explored how solvent dynamics change during the course of a reaction with solutes that encounter a wide range of configurations. Here, we use quantum simulation methods to explore the solvent dynamics during a solution-phase bond-breaking reaction: the photodissociation of Na2+ in liquid Ar. We find that the solute experiences a small number of distinct solvent environments that change in a discrete fashion as the bond lengthens. In characterizing the solvent environments, we show also that linear response fails by all measures, even when nonstationarity of solvent dynamics is considered. This observation of distinct solvent response environments with a solvent that can undergo only translational motions highlights the complexity of solute-solvent interactions, but that there are only a few environments gives hope to the idea that solvation dynamics can be understood for solution-phase reactions that explore a wide configuration space.
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Affiliation(s)
- Andy Vong
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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12
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Park SJ, Schwartz BJ. Understanding the Temperature Dependence and Finite Size Effects in Ab Initio MD Simulations of the Hydrated Electron. J Chem Theory Comput 2022; 18:4973-4982. [PMID: 35834750 DOI: 10.1021/acs.jctc.2c00335] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The hydrated electron is of interest to both theorists and experimentalists as a paradigm solution-phase quantum system. Although the bulk of the theoretical work studying the hydrated electron is based on mixed quantum/classical (MQC) methods, recent advances in computer power have allowed several attempts to study this object using ab initio methods. The difficulty with employing ab initio methods for this system is that even with relatively inexpensive quantum chemistry methods such as density functional theory (DFT), such calculations are still limited to at most a few tens of water molecules and only a few picoseconds duration, leaving open the question as to whether the calculations are converged with respect to either system size or dynamical fluctuations. Moreover, the ab initio simulations of the hydrated electron that have been published to date have provided only limited analysis. Most works calculate the electron's vertical detachment energy, which can be compared to experiment, and occasionally the electronic absorption spectrum is also computed. Structural features, such as pair distribution functions, are rare in the literature, with the majority of the structural analysis being simple statements that the electron resides in a cavity, which are often based only on a small number of simulation snapshots. Importantly, there has been no ab initio work examining the temperature-dependent behavior of the hydrated electron, which has not been satisfactorily explained by MQC simulations. In this work, we attempt to remedy this situation by running DFT-based ab initio simulations of the hydrated electron as a function of both box size and temperature. We show that the calculated properties of the hydrated electron are not converged even with simulation sizes up to 128 water molecules and durations of several tens of picoseconds. The simulations show significant changes in the water coordination and solvation structure with box size. Our temperature-dependent simulations predict a red-shift of the absorption spectrum (computed using TD-DFT with an optimally tuned range-separated hybrid functional) with increasing temperature, but the magnitude of the predicted red-shift is larger than that observed experimentally, and the absolute position of the calculated spectra are off by over half an eV. The spectral red-shift at high temperatures is accompanied by both a partial loss of structure of the electron's central cavity and an increased radius of gyration that pushes electron density onto and beyond the first solvation shell. Overall, although ab initio simulations can provide some insights into the temperature-dependent behavior of the hydrated electron, the simulation sizes and level of quantum chemistry theory that are currently accessible are inadequate for correctly describing the experimental properties of this fascinating object.
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Affiliation(s)
- Sanghyun J Park
- Department of Chemistry and Biochemistry University of California,Los Angeles Los Angeles California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry University of California,Los Angeles Los Angeles California 90095-1569, United States
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13
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Wu ECK, Salamat CZ, Tolbert SH, Schwartz BJ. Molecular Dynamics Study of the Thermodynamics of Integer Charge Transfer vs Charge-Transfer Complex Formation in Doped Conjugated Polymers. ACS Appl Mater Interfaces 2022; 14:26988-27001. [PMID: 35657331 DOI: 10.1021/acsami.2c06449] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Molecular dopants such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) can interact with conjugated polymers such as poly(3-hexylthiophene-2,5-diyl) (P3HT) in two different ways: they can undergo integer charge transfer (ICT) or they can form a partial-charge-transfer complex (CTC). Both are seen experimentally, but the CTC has been challenging to characterize, making it difficult to answer questions such as the following. Which polymorph is more stable? Do they have similar barriers for formation? Is there a thermodynamic route to convert one to the other? Here, we study the structure and the thermodynamics of bulk F4TCNQ-doped P3HT with all-atom molecular dynamics simulations, using thermodynamic integration to calculate the relative free energies. We find that the ICT and CTC polymorphs have similar thermodynamic stabilities. The barrier to create the ICT polymorph, however, is lower than that to make the CTC polymorph, because the ICT polymorph has a small critical nucleus, but the critical nucleus for the CTC polymorph is larger than what we can simulate. Moreover, simulated thermal annealing shows that the activation barrier for converting the CTC polymorph to the ICT polymorph is relatively modest. Overall, the simulations explain both the observed structures and the thermodynamics of F4TCNQ-doped P3HT and offer guidelines for targeting the production of a desired polymorph for different applications.
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Affiliation(s)
- Eric Chih-Kuan Wu
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, California 90095-1569, United States
| | - Charlene Z Salamat
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, California 90095-1569, United States
| | - Sarah H Tolbert
- Departments of Chemistry and Biochemistry and Materials Science and Engineering University of California, Los Angeles Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles, California 90095-1569, United States
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14
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Narvaez WA, Park SJ, Schwartz BJ. Hydrated Electrons in High-Concentration Electrolytes Interact with Multiple Cations: A Simulation Study. J Phys Chem B 2022; 126:3748-3757. [PMID: 35544344 DOI: 10.1021/acs.jpcb.2c01501] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Experimental studies have demonstrated that the hydrated electron's absorption spectrum undergoes a concentration-dependent blue-shift in the presence of electrolytes such as NaCl. The blue-shift increases roughly linearly at low salt concentration but saturates as the solubility limit of the salt is approached. Previous attempts to understand the origin of the concentration-dependent spectral shift using molecular simulation have only examined the interaction between the hydrated electron and a single sodium cation, and these simulations predicted a spectral blue-shift that was an order of magnitude larger than that seen experimentally. Thus, in this paper, we first explore the reasons for the exaggerated spectral blue-shift when a simulated hydrated electron interacts with a single Na+. We find that the issue arises from nonpairwise additivity of the Na+-e- and H2O-e- pseudopotentials used in the simulation. This effect arises because the solvating water molecules donate charge into the empty orbitals of Na+, lowering the effective charge of the cation and thus reducing the excess electron-cation interaction. Careful analysis shows, however, that although this nonpairwise additivity changes the energetics of the electron-Na+ interaction, the forces between the electron, Na+, and water are unaffected, so that mixed quantum/classical (MQC) simulations produce the correct structure and dynamics. With this in hand, we then use MQC simulations to explore the behavior of the hydrated electron as an explicit function of NaCl salt concentration. We find that the simulations correctly reproduce the observed experimental spectral shifting behavior. The reason for the spectral shift is that as the electrolyte concentration increases, the average number of cations simultaneously interacting in contact pairs with the hydrated electron increases from 1.0 at low concentrations to ∼2.5 near the saturation limit. As the number of cations that interact with the electron increases, the cation/electron interactions becomes slightly weaker, so that the corresponding Na+-e- distance increases with increasing salt concentration. We also find that the dielectric constant of the solution plays little role in the observed spectroscopy, so that the electrolyte-dependent spectral shifts of the hydrated electron are directly related to the concentration-dependent number of closely interacting cations.
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Affiliation(s)
- Wilberth A Narvaez
- Department of Chemistry and Biochemistry, University of California, Los Angeles Los Angeles, California 90095-1569 United States
| | - Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles Los Angeles, California 90095-1569 United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles Los Angeles, California 90095-1569 United States
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Park SJ, Narvaez WA, Schwartz BJ. How Water-Ion Interactions Control the Formation of Hydrated Electron:Sodium Cation Contact Pairs. J Phys Chem B 2021; 125:13027-13040. [PMID: 34806385 DOI: 10.1021/acs.jpcb.1c08256] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although solvated electrons are a perennial subject of interest, relatively little attention has been paid to the way they behave in aqueous electrolytes. Experimentally, it is known that the hydrated electron's (eaq-) absorption spectrum shifts to the blue in the presence of salts, and the magnitude of the shift depends on the ion concentration and the identities of both the cation and anion. Does the blue-shift result from some type of dielectric effect from the bulk electrolyte, or are there specific interactions between the hydrated electron and ions in solution? Previous work has suggested that eaq- forms contact pairs with aqueous ions such as Na+, leading to the question of what controls the stability of such contact pairs and their possible connection to the observed spectroscopy. In this work, we use mixed quantum/classical simulations to examine the nature of Na+:e- contact pairs in water, using a novel method for quantum umbrella sampling to construct eaq--ion potentials of mean force (PMF). We find that the nature of the contact pair PMF depends sensitively on the choice of the classical interactions used to describe the Na+-water interactions. When the ion-water interactions are slightly stronger, the corresponding cation:e- contact pairs form at longer distances and become free energetically less stable. We show that this is because there is a delicate balance between solvation of the cation, solvation of eaq- and the direct electronic interaction between the cation and the electron, so that small changes in this balance lead to large changes in the formation and stability of e--ion contact pairs. In particular, strengthening the ion-water interactions helps to maintain a favorable local solvation environment around Na+, which in turn forces water molecules in the first solvation shell of the cation to be unfavorably oriented toward the electron in a contact pair; stronger solvation of the cation also reduces the electronic overlap of eaq- with Na+. We also find that the calculated spectra of different models of Na+:e- contact pairs do not shift monotonically with cation-electron distance, and that the calculated spectral shifts are about an order of magnitude larger than experiment, suggesting that isolated contact pairs are not the sole explanation for the blue-shift of the hydrated electron's spectrum in the presence of electrolytes.
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Affiliation(s)
- Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Wilberth A Narvaez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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Narvaez WA, Schwartz BJ. Ab Initio Simulations of Poorly and Well Equilibrated (CH 3CN) n- Cluster Anions: Assigning Experimental Photoelectron Peaks to Surface-Bound Electrons and Solvated Monomer and Dimer Anions. J Phys Chem A 2021; 125:7685-7693. [PMID: 34432443 DOI: 10.1021/acs.jpca.1c05855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Excess electrons in liquid acetonitrile are of particular interest because they exist in two different forms in equilibrium: they can be present as traditional solvated electrons in a cavity, and they can form some type of solvated molecular anion. Studies of small acetonitrile cluster anions in the gas phase show two isomers with distinct vertical detachment energies, and it is tempting to presume that the two gas-phase cluster anion isomers are precursors of the two excess electron species present in bulk solution. In this paper, we perform DFT-based ab initio molecular dynamics simulations of acetonitrile cluster anions to understand the electronic species that are present and why they have different binding energies. Using a long-range-corrected density functional that was optimally tuned to describe acetonitrile cluster anion structures, we have theoretically explored the chemistry of (CH3CN)n- cluster anions with sizes n = 5, 7, and 10. Because the temperature of the experimental cluster anions is not known, we performed two sets of simulations that investigated how the way in which the cluster anions are prepared affects the excess electron binding motif: one set of simulations simply attached excess electrons to neutral (CH3CN)n clusters, providing little opportunity for the clusters to relax in the presence of the excess electron, while the other set allowed the cluster anions to thermally equilibrate near room temperature. We find that both sets of simulations show three distinct electron binding motifs: electrons can attach to the surface of the cluster (dipole-bound) or be present either as solvated monomer anions, CH3CN-, or as solvated molecular dimer anions, (CH3CN)2-. All three species have higher binding energies at larger cluster sizes. Thermal equilibration strongly favors the formation of the valence-bound molecular anions relative to surface-bound excess electrons, and the dimer anion becomes more stable than the monomer anion and surface-bound species as the cluster size increases. The calculated photoelectron spectra from our simulations in which there was poor thermal equilibration are in good agreement with experiment, suggesting assignment of the two experimental cluster anion isomers as the surface-bound electron and the solvated molecular dimer anion. The simulations also suggest that the shoulder seen experimentally on the low-energy isomer's detachment peak is not part of a vibronic progression but instead results from molecular monomer anions. Nowhere in the size range that we explore do we see evidence for a nonvalence, cavity-bound interior-solvated electron, indicating that this species is likely only accessible at larger sizes with good thermal equilibration.
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Affiliation(s)
- Wilberth A Narvaez
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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Voss MG, Challa JR, Scholes DT, Yee PY, Wu EC, Liu X, Park SJ, León Ruiz O, Subramaniyan S, Chen M, Jenekhe SA, Wang X, Tolbert SH, Schwartz BJ. Driving Force and Optical Signatures of Bipolaron Formation in Chemically Doped Conjugated Polymers. Adv Mater 2021; 33:e2000228. [PMID: 33296113 DOI: 10.1002/adma.202000228] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 10/11/2020] [Indexed: 06/12/2023]
Abstract
Molecular dopants are often added to semiconducting polymers to improve electrical conductivity. However, the use of such dopants does not always produce mobile charge carriers. In this work, ultrafast spectroscopy is used to explore the nature of the carriers created following doping of conjugated push-pull polymers with both F4 TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and FeCl3 . It is shown that for one particular push-pull material, the charge carriers created by doping are entirely non-conductive bipolarons and not single polarons, and that transient absorption spectroscopy following excitation in the infrared can readily distinguish the two types of charge carriers. Based on density functional theory calculations and experiments on multiple push-pull conjugated polymers, it is argued that the size of the donor push units determines the relative stabilities of polarons and bipolarons, with larger donor units stabilizing the bipolarons by providing more area for two charges to co-reside.
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Affiliation(s)
- Matthew G Voss
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - J Reddy Challa
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - D Tyler Scholes
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Patrick Y Yee
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Eric C Wu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Xiao Liu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Omar León Ruiz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Selvam Subramaniyan
- Department of Chemical Engineering and Department of Chemistry, University of Washington, Seattle, WA, 98195-1750, USA
| | - Mengdan Chen
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Samson A Jenekhe
- Department of Chemical Engineering and Department of Chemistry, University of Washington, Seattle, WA, 98195-1750, USA
| | - Xiaolin Wang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-8352, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095-1595, USA
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-8352, USA
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Pettitt BM, Schwartz BJ, Sterpone F, Túri L, Willard AP. Tribute to Peter J. Rossky. J Phys Chem B 2020; 124:10591-10593. [DOI: 10.1021/acs.jpcb.0c09810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Vong A, Widmer DR, Schwartz BJ. Nonequilibrium Solvent Effects during Photodissociation in Liquids: Dynamical Energy Surfaces, Caging, and Chemical Identity. J Phys Chem Lett 2020; 11:9230-9238. [PMID: 33064478 DOI: 10.1021/acs.jpclett.0c02515] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the gas phase, potential energy surfaces can be used to provide insight into the details of photochemical reaction dynamics. In solution, however, it is unclear what potential energy surfaces, if any, can be used to describe even simple chemical reactions such as the photodissociation of a diatomic solute. In this paper, we use mixed quantum/classical (MQC) molecular dynamics (MD) to study the photodissociation of Na2+ in both liquid Ar and liquid tetrahydrofuran (THF). We examine both the gas-phase potential surfaces and potentials of mean force (PMF), which assume that the solvent remains at equilibrium with the solute throughout the photodissociation process and show that neither resemble a nonequilibrium dynamical energy surface that is generated by taking the time integral of work. For the photodissociation of Na2+ in liquid Ar, the dynamical energy surface shows clear signatures of solvent caging, and the degree of caging is directly related to the mass of the solvent atoms. For Na2+ in liquid THF, local specific interactions between the solute and solvent lead to changes in chemical identity that create a kinetic trap that effectively prevents the molecule from dissociating. The results show that nonequilibrium effects play an important role even in simple solution-phase reactions, requiring the use of dynamical energy surface to understand such chemical events.
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Affiliation(s)
- Andy Vong
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Devon R Widmer
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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20
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Abstract
Despite its importance in electron transfer reactions and radiation chemistry, there has been disagreement over the fundamental nature of the hydrated electron, such as whether or not it resides in a cavity. Mixed quantum/classical simulations of the hydrated electron give different structures depending on the pseudopotential employed, and ab initio models of computational necessity use small numbers of water molecules and/or provide insufficient statistics to compare to experimental observables. A few years ago, Kumar et al. (J. Phys. Chem. A 2015, 119, 9148) proposed a minimalist ab initio model of the hydrated electron with only a small number of explicitly treated water molecules plus a polarizable continuum model (PCM). They found that the optimized geometry had four waters arranged tetrahedrally around a central cavity, and that the calculated vertical detachment energy and radius of gyration agreed well with experiment, results that were largely independent of the level of theory employed. The model, however, is based on a fixed structure at 0 K and does not explicitly incorporate entropic contributions or the thermal fluctuations that should be associated with the room-temperature hydrated electron. Thus, in this paper, we extend the model of Kumar et al. by running Born-Oppenheimer molecular dynamics (BOMD) of a small number of water molecules with an excess electron plus PCM at room temperature. We find that when thermal fluctuations are introduced, the level of theory chosen becomes critical enough when only four waters are used that one of the waters dissociates from the cluster with certain density functionals. Moreover, even with an optimally tuned range-separated hybrid functional, at room temperature the tetrahedral orientation of the 0 K first-shell waters is entirely lost and the central cavity collapses, a process driven by the fact that the explicit water molecules prefer to make H-bonds with each other more than with the excess electron. The resulting average structure is quite similar to that produced by a noncavity mixed quantum/classical model, so that the minimalist 4-water BOMD models suffer from problems similar to those of noncavity models, such as predicting the wrong sign of the hydrated electron's molar solvation volume. We also performed BOMD with 16 explicit water molecules plus an extra electron and PCM. We find that the inclusion of an entire second solvation shell of explicit water leads to little change in the outcome from when only four waters were used. In fact, the 16-water simulations behave much like those of water cluster anions, in which the electron localizes at the cluster surface, showing that PCM is not acceptable for use in minimalist models to describe the behavior of the bulk hydrated electron. For both the 4- and 16-water models, we investigate how the introduction of thermal motions alters the predicted absorption spectrum, vertical detachment energy, and resonance Raman spectrum of the simulated hydrated electron. We also present a set of structural criteria that can be used to numerically determine how cavity-like (or not) a particular hydrated electron model is. All of the results emphasize that the hydrated electron is a statistical object whose properties are inadequately captured using only a small number of explicit waters, and that a proper treatment of thermal fluctuations is critical to understanding the hydrated electron's chemical and physical behavior.
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Affiliation(s)
- Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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Widmer DR, Schwartz BJ. The Role of the Solvent in the Condensed-Phase Dynamics and Identity of Chemical Bonds: The Case of the Sodium Dimer Cation in THF. J Phys Chem B 2020; 124:6603-6616. [PMID: 32603114 DOI: 10.1021/acs.jpcb.0c03298] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
When a solute molecule is placed in solution, is it acceptable to presume that its electronic structure is essentially the same as that in the gas phase? In this paper, we address this question from a simulation perspective for the case of the sodium dimer cation (Na2+) molecule in both liquid Ar and liquid tetrahydrofuran (THF). In previous work, we showed that, when local specific interactions between a solute and solvent are energetically on the order of a hydrogen bond, the solvent can become part of the chemical identity of the solute. Here, using mixed quantum/classical molecular dynamics simulations, we see that, for the Na2+ molecule, solute-solvent interactions lead to two stable, chemically distinct coordination states (Na(THF)4-Na(THF)5+ and Na(THF)5-Na(THF)5+) that are not only stable themselves as gas-phase molecules but that also have a completely new electronic structure with important implications for the excited-state photodissociation of this molecule in the condensed phase. Furthermore, we show through a set of comparative classical simulations that treating the solute's bonding electron explicitly quantum mechanically is necessary to understand both the ground-state dynamics and chemical identity of this simple diatomic molecule; even use of the quantum-derived potential of mean force is insufficient to describe the behavior of the molecule classically. Finally, we calculate the results of a proposed transient hole-burning experiment that could be used to spectroscopically disentangle the presence of the different coordination states.
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Affiliation(s)
- Devon R Widmer
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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Aubry TJ, Winchell KJ, Salamat CZ, Basile VM, Lindemuth JR, Stauber JM, Axtell JC, Kubena RM, Phan MD, Bird MJ, Spokoyny AM, Tolbert SH, Schwartz BJ. Tunable Dopants with Intrinsic Counterion Separation Reveal the Effects of Electron Affinity on Dopant Intercalation and Free Carrier Production in Sequentially Doped Conjugated Polymer Films. Adv Funct Mater 2020; 30:2001800. [PMID: 32684909 PMCID: PMC7357248 DOI: 10.1002/adfm.202001800] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/02/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
Carrier mobility in doped conjugated polymers is limited by Coulomb interactions with dopant counterions. This complicates studying the effect of the dopant's oxidation potential on carrier generation because different dopants have different Coulomb interactions with polarons on the polymer backbone. Here, dodecaborane (DDB)-based dopants are used, which electrostatically shield counterions from carriers and have tunable redox potentials at constant size and shape. DDB dopants produce mobile carriers due to spatial separation of the counterion, and those with greater energetic offsets produce more carriers. Neutron reflectometry indicates that dopant infiltration into conjugated polymer films is redox-potential-driven. Remarkably, X-ray scattering shows that despite their large 2-nm size, DDBs intercalate into the crystalline polymer lamellae like small molecules, indicating that this is the preferred location for dopants of any size. These findings elucidate why doping conjugated polymers usually produces integer, rather than partial charge transfer: dopant counterions effectively intercalate into the lamellae, far from the polarons on the polymer backbone. Finally, it is shown that the IR spectrum provides a simple way to determine polaron mobility. Overall, higher oxidation potentials lead to higher doping efficiencies, with values reaching 100% for driving forces sufficient to dope poorly crystalline regions of the film.
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Affiliation(s)
- Taylor J. Aubry
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - K. J. Winchell
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Charlene Z. Salamat
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Victoria M. Basile
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | | | - Julia M. Stauber
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Jonathan C. Axtell
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Rebecca M. Kubena
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Minh D. Phan
- Neutron Scattering DivisionOak Ridge National LaboratoryOak RidgeTN37831USA
| | - Matthew J. Bird
- Chemistry DepartmentBrookhaven National LaboratoryUptonNY11973USA
| | - Alexander M. Spokoyny
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesCA90095‐7227USA
| | - Sarah H. Tolbert
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesCA90095‐7227USA
- Department of Materials Science and EngineeringUniversity of California, Los AngelesLos AngelesCA90095‐1595USA
| | - Benjamin J. Schwartz
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesCA90095‐7227USA
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Glover WJ, Schwartz BJ. The Fluxional Nature of the Hydrated Electron: Energy and Entropy Contributions to Aqueous Electron Free Energies. J Chem Theory Comput 2020; 16:1263-1270. [PMID: 31914315 DOI: 10.1021/acs.jctc.9b00496] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There has been a great deal of recent controversy over the structure of the hydrated electron and whether it occupies a cavity or contains a significant number of interior waters (noncavity). The questions we address in this work are, from a free energy perspective, how different are these proposed structures? Do the different structures all lie along a single continuum, or are there significant differences (i.e., free energy barriers) between them? To address these questions, we have performed a series of one-electron calculations using umbrella sampling with quantum biased molecular dynamics along a coordinate that directly reflects the number of water molecules in the hydrated electron's interior. We verify that a standard cavity model of the hydrated electron behaves essentially as a hard sphere: the model is dominated by repulsion at short range such that water is expelled from a local volume around the electron, leading to a water solvation shell like that of a pseudohalide ion. The repulsion is much larger than thermal energies near room temperature, explaining why such models exhibit properties with little temperature dependence. On the other hand, our calculations reveal that a noncavity model is highly fluxional, meaning that thermal motions cause the number of interior waters to fluctuate from effectively zero (i.e., a cavity-type electron) to potentially above the bulk water density. The energetic contributions in the noncavity model are still repulsive in the sense that they favor cavity formation, so the fluctuations in structure are driven largely by entropy: the entropic cost for expelling water from a region of space is large enough that some water is still driven into the electron's interior. As the temperature is lowered and entropy becomes less important, the noncavity electron's structure is predicted to become more cavity-like, consistent with the observed temperature dependence of the hydrated electron's properties. Thus, we argue that although the specific noncavity model we study overestimates the preponderance of fluctuations involving interior water molecules, with appropriate refinements to correctly capture the true average number of interior waters and molar solvation volume, a fluxional model likely makes the most sense for understanding the various experimental properties of the hydrated electron.
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Affiliation(s)
- William J Glover
- NYU Shanghai , 1555 Century Ave. , Pudong, Shanghai , China 200122.,NYU-ECNU Center for Computational Chemistry at NYU Shanghai , 3663 Zhongshang Road , Shanghai , China 200062.,Department of Chemistry , New York University , New York , New York 10003 , United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry , University of California, Los Angeles , 607 Charles E. Young Drive East , Los Angeles , California 90095-1569 , United States
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Abstract
Despite the fact that molecular doping of semiconducting polymers has emerged as a valuable strategy for improving the performance of organic electronic devices, the fundamental dopant-polymer interactions are not fully understood. Here we use 2-D grazing incidence wide-angle X-ray scattering (GIWAXS) to demonstrate that adding oxidizing small-molecule dopants, such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and FeCl3, into the amorphous conjugated polymer, regiorandom poly(3-hexylthiophene-2,5-diyl) (RRa-P3HT), improves polymer ordering and induces a change in domain orientation from isotropic to mostly edge-on. Doping thus causes RRa-P3HT to behave similarly to the more ordered regioregular P3HT. By comparing the optical, electrical, and structural properties of RRa-P3HT films doped with F4TNCQ and FeCl3 and those infiltrated with 7,7,8,8-tetracyanoquinodimethane (TCNQ), which occupies a similar volume as F4TCNQ but does not dope RRa-P3HT, we show that the increased ordering results not from the ability of the dopant to fill space but instead from the need to delocalize charge on the polymer in more than one dimension.
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Affiliation(s)
- Patrick Y Yee
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - D Tyler Scholes
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095-1595, United States
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Aubry TJ, Axtell JC, Basile VM, Winchell KJ, Lindemuth JR, Porter TM, Liu JY, Alexandrova AN, Kubiak CP, Tolbert SH, Spokoyny AM, Schwartz BJ. Dodecaborane-Based Dopants Designed to Shield Anion Electrostatics Lead to Increased Carrier Mobility in a Doped Conjugated Polymer. Adv Mater 2019; 31:e1805647. [PMID: 30672037 DOI: 10.1002/adma.201805647] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/07/2018] [Indexed: 06/09/2023]
Abstract
One of the most effective ways to tune the electronic properties of conjugated polymers is to dope them with small-molecule oxidizing agents, creating holes on the polymer and molecular anions. Undesirably, strong electrostatic attraction from the anions of most dopants localizes the holes created on the polymer, reducing their mobility. Here, a new strategy utilizing a substituted boron cluster as a molecular dopant for conjugated polymers is employed. By designing the cluster to have a high redox potential and steric protection of the core-localized electron density, highly delocalized polarons with mobilities equivalent to films doped with no anions present are obtained. AC Hall effect measurements show that P3HT films doped with these boron clusters have conductivities and polaron mobilities roughly an order of magnitude higher than films doped with F4 TCNQ, even though the boron-cluster-doped films have poor crystallinity. Moreover, the number of free carriers approximately matches the number of boron clusters, yielding a doping efficiency of ≈100%. These results suggest that shielding the polaron from the anion is a critically important aspect for producing high carrier mobility, and that the high polymer crystallinity required with dopants such as F4 TCNQ is primarily to keep the counterions far from the polymer backbone.
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Affiliation(s)
- Taylor J Aubry
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Jonathan C Axtell
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Victoria M Basile
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - K J Winchell
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | | | - Tyler M Porter
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Ji-Yuan Liu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- Key Laboratory for Advanced Materials, Center for Computational Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Clifford P Kubiak
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Alexander M Spokoyny
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
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26
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Voss MG, Scholes DT, Challa JR, Schwartz BJ. Ultrafast transient absorption spectroscopy of doped P3HT films: distinguishing free and trapped polarons. Faraday Discuss 2019; 216:339-362. [PMID: 31038132 DOI: 10.1039/c8fd00210j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
It is generally presumed that the vast majority of carriers created by chemical doping of semiconducting polymer films are coulombically trapped by the counteranion, with only a small fraction that are free and responsible for the increased conductivity essential for organic electronic applications. At higher doping levels, it is also possible for bipolarons to form, which are expected to be less conductive than single polarons. Unfortunately, there is no simple way to distinguish free polarons, trapped polarons and bipolarons using steady-state spectroscopy. Thus, in this work, we use ultrafast transient absorption spectroscopy to study the dynamics of polarons in 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TNCQ)-doped films of poly(3-hexylthiophene-2,5-diyl) (P3HT) as a function of dopant concentration and excitation wavelength. When exciting on the red side of the polaron P1 transition, our transient absorption spectra and kinetics match well with what is expected for free 2-D-delocalized polarons; the measurements are not consistent with a recent theory of doped conjugated polymer electronic structure that suggests that the half-filled state lies deeper in the conduction band rather than in the bandgap. As we tune the excitation wavelength to the blue, our measurements reveal an increasing amount of slower transient kinetics that are consistent with the presence of coulombically-trapped polarons rather than bipolarons. Taking advantage of their distinct ultrafast relaxation kinetics as a type of action spectroscopy, we are able to extract the steady-state absorption spectra of free and trapped polarons as a function of dopant concentration. By comparing the results to theoretical models, we determine that in F4TCNQ-doped P3HT films, trapped polarons sit ∼0.4 nm away from the anion while free polarons reside between 0.7 and 0.9 nm from the counteranion. Perhaps counterintuitively, the ratio of trapped to free polarons increases at higher doping levels, an observation that is consistent with a plateau in the concentration-dependent conductivity of F4TCNQ-doped P3HT films.
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Affiliation(s)
- Matthew G Voss
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - D Tyler Scholes
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - J Reddy Challa
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
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27
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Zho CC, Vlček V, Neuhauser D, Schwartz BJ. Thermal Equilibration Controls H-Bonding and the Vertical Detachment Energy of Water Cluster Anions. J Phys Chem Lett 2018; 9:5173-5178. [PMID: 30129761 DOI: 10.1021/acs.jpclett.8b02152] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
One of the outstanding puzzles in the photoelectron spectroscopy of water anion clusters, which serve as precursors to the hydrated electron, is that the excess electron has multiple vertical detachment energies (VDEs), with different groups seeing different distributions of VDEs. We have studied the photoelectron spectroscopy of water cluster anions using simulation techniques designed to mimic the different ways that water cluster anions are produced experimentally. Our simulations take advantage of density functional theory-based Born-Oppenheimer molecular dynamics with an optimally tuned range-separated hybrid functional that is shown to give outstanding accuracy for calculating electron binding energies for this system. We find that our simulations are able to accurately reproduce the experimentally observed VDEs for cluster anions of different sizes, with different VDE distributions observed depending on how the water cluster anions are prepared. For cluster anion sizes up to 20 water molecules, we see that the excess electron always resides on the surface of the cluster and that the different discrete VDEs result from the discrete number of hydrogen bonds made to the electron by water molecules on the surface. Clusters that are less thermally equilibrated have surface waters that tend to make single H-bonds to the electron, resulting in lower VDEs, while clusters that are more thermally equilibrated have surface waters that prefer to make two H-bonds to the electron, resulting in higher VDEs.
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Affiliation(s)
- Chen-Chen Zho
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095-1569 , United States
| | - Vojtěch Vlček
- Department of Chemistry and Biochemistry , University of California, Santa Barbara , Santa Barbara , California 93106 , United States
| | - Daniel Neuhauser
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095-1569 , United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095-1569 , United States
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28
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Farr EP, Zho CC, Challa JR, Schwartz BJ. Erratum: "Temperature dependence of the hydrated electron's excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy" [J. Chem. Phys. 147, 074504 (2017)]. J Chem Phys 2017; 147:139903. [PMID: 28987099 DOI: 10.1063/1.5006797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Erik P Farr
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | - Chen-Chen Zho
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | - Jagannadha R Challa
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
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29
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Farr EP, Zho CC, Challa JR, Schwartz BJ. Temperature dependence of the hydrated electron’s excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy. J Chem Phys 2017; 147:074504. [DOI: 10.1063/1.4985906] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Erik P. Farr
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
| | - Chen-Chen Zho
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
| | - Jagannadha R. Challa
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
| | - Benjamin J. Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
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30
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Zho CC, Farr EP, Glover WJ, Schwartz BJ. Temperature dependence of the hydrated electron’s excited-state relaxation. I. Simulation predictions of resonance Raman and pump-probe transient absorption spectra of cavity and non-cavity models. J Chem Phys 2017; 147:074503. [DOI: 10.1063/1.4985905] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Chen-Chen Zho
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California,
90095-1569, USA
| | - Erik P. Farr
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California,
90095-1569, USA
| | - William J. Glover
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California,
90095-1569, USA
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
- NYU Shanghai, 1555 Century Avenue,
Shanghai 200135, China
| | - Benjamin J. Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California,
90095-1569, USA
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31
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Zho CC, Schwartz BJ. Time-Resolved Photoelectron Spectroscopy of the Hydrated Electron: Comparing Cavity and Noncavity Models to Experiment. J Phys Chem B 2016; 120:12604-12614. [PMID: 27973828 DOI: 10.1021/acs.jpcb.6b07852] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Chen-Chen Zho
- Department of Chemistry and
Biochemistry University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J. Schwartz
- Department of Chemistry and
Biochemistry University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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32
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Abstract
The hydrated electron, e-(aq), has often served as a model system to understand the influence of condensed-phase environments on electronic structure and dynamics. Despite over 50 years of study, however, the basic structure of e-(aq) is still the subject of controversy. In particular, the structure of e-(aq) was long assumed to be an electron localized within a solvent cavity, in a manner similar to halide solvation. Recently, however, we suggested that e-(aq) occupies a region of enhanced water density with little or no discernible cavity. The potential we developed was only subtly different from those that give rise to a cavity solvation motif, which suggests that the driving forces for noncavity solvation involve subtle electron-water attractive interactions at close distances. This leads to the question of how dispersion interactions are treated in simulations of the hydrated electron. Most dispersion potentials are ad hoc or are not designed to account for the type of close-contact electron-water overlap that might occur in the condensed phase, and where short-range dynamic electron correlation is important. To address this, in this paper we develop a procedure to calculate the potential energy surface between a single water molecule and an excess electron with high-level CCSD(T) electronic structure theory. By decomposing the electron-water potential into its constituent energetic contributions, we find that short-range electron correlation provides an attraction of comparable magnitude to the mean-field interactions between the electron and water. Furthermore, we find that by reoptimizing a popular cavity-forming one-electron model potential to better capture these attractive short-range interactions, the enhanced description of correlation predicts a noncavity e-(aq) with calculated properties in better agreement with experiment. Although much attention has been placed on the importance of long-range dispersion interactions in water cluster anions, our study reveals that largely unexplored short-range correlation effects are crucial in dictating the solvation structure of the condensed-phase hydrated electron.
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Affiliation(s)
- William J Glover
- NYU-ECNU Center for Computational Chemistry, New York University Shanghai , Shanghai, 200122, China.,Department of Chemistry, New York University , New York, New York 10003, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States
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33
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Abstract
The properties of the hydrated electron at the air/water interface are computed for both a cavity and a noncavity model using mixed quantum/classical molecular dynamics simulation. We take advantage of our recently developed formalism for umbrella sampling with a restrained quantum expectation value to calculate free-energy profiles of the hydrated electron's position relative to the water surface. We show that it is critical to use an instantaneous description of the air/water interface rather than the Gibbs' dividing surface to obtain accurate potentials of mean force. We find that noncavity electrons, which prefer to encompass several water molecules, avoid the interface where water molecules are scarce. In contrast, cavity models of the hydrated electron, which prefer to expel water, have a local free-energy minimum near the interface. When the cavity electron occupies this minimum, its absorption spectrum is quite red-shifted, its binding energy is significantly lowered, and its dynamics speed up quite a bit compared with the bulk, features that have not been found by experiment. The surface activity of the electron therefore serves as a useful test of cavity versus noncavity electron solvation.
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Affiliation(s)
- Jennifer R Casey
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - William J Glover
- NYU-ECNU Center for Computational Chemistry, New York University Shanghai , Shanghai 200122, China
- Department of Chemistry, New York University , New York, New York 10003, United States
- Department of Chemistry, East China Normal University , Shanghai 200062, China
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34
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Huber RC, Ferreira AS, Aguirre JC, Kilbride D, Toso DB, Mayoral K, Zhou ZH, Kopidakis N, Rubin Y, Schwartz BJ, Mason TG, Tolbert SH. Structure and Conductivity of Semiconducting Polymer Hydrogels. J Phys Chem B 2016; 120:6215-24. [DOI: 10.1021/acs.jpcb.6b02202] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rachel C. Huber
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Amy S. Ferreira
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Jordan C. Aguirre
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Daniel Kilbride
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Daniel B. Toso
- Department of Microbiology, Immunology & Molecular Genetics, and Biomedical Engineering Program, UCLA, 609 Charles E. Young Drive South, Los Angeles, California 90095, United States
| | - Kenny Mayoral
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Z. Hong Zhou
- Department of Microbiology, Immunology & Molecular Genetics, and Biomedical Engineering Program, UCLA, 609 Charles E. Young Drive South, Los Angeles, California 90095, United States
- California NanoSystems
Institute, UCLA, 570 Westwood Plaza, Los Angeles, California 90095, United States
| | - Nikos Kopidakis
- Chemical and Nanoscience
Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Yves Rubin
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Benjamin J. Schwartz
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
- California NanoSystems
Institute, UCLA, 570 Westwood Plaza, Los Angeles, California 90095, United States
| | - Thomas G. Mason
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Sarah H. Tolbert
- Department
of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
- California NanoSystems
Institute, UCLA, 570 Westwood Plaza, Los Angeles, California 90095, United States
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35
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Lin H, Zeng J, Xie R, Schulz MJ, Tedesco R, Qu J, Erhard KF, Mack JF, Raha K, Rendina AR, Szewczuk LM, Kratz PM, Jurewicz AJ, Cecconie T, Martens S, McDevitt PJ, Martin JD, Chen SB, Jiang Y, Nickels L, Schwartz BJ, Smallwood A, Zhao B, Campobasso N, Qian Y, Briand J, Rominger CM, Oleykowski C, Hardwicke MA, Luengo JI. Discovery of a Novel 2,6-Disubstituted Glucosamine Series of Potent and Selective Hexokinase 2 Inhibitors. ACS Med Chem Lett 2016; 7:217-22. [PMID: 26985301 DOI: 10.1021/acsmedchemlett.5b00214] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 12/27/2015] [Indexed: 12/13/2022] Open
Abstract
A novel series of potent and selective hexokinase 2 (HK2) inhibitors, 2,6-disubstituted glucosamines, has been identified based on HTS hits, exemplified by compound 1. Inhibitor-bound crystal structures revealed that the HK2 enzyme could adopt an "induced-fit" conformation. The SAR study led to the identification of potent HK2 inhibitors, such as compound 34 with greater than 100-fold selectivity over HK1. Compound 25 inhibits in situ glycolysis in a UM-UC-3 bladder tumor cell line via (13)CNMR measurement of [3-(13)C]lactate produced from [1,6-(13)C2]glucose added to the cell culture.
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Affiliation(s)
- Hong Lin
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Jin Zeng
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Ren Xie
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Mark J. Schulz
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Rosanna Tedesco
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Junya Qu
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Karl F. Erhard
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - James F. Mack
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Kaushik Raha
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Alan R. Rendina
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Lawrence M. Szewczuk
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Patricia M. Kratz
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Anthony J. Jurewicz
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Ted Cecconie
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Stan Martens
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Patrick J. McDevitt
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - John D. Martin
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Stephenie B. Chen
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Yong Jiang
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Leng Nickels
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Benjamin J. Schwartz
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Angela Smallwood
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Baoguang Zhao
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Nino Campobasso
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Yanqiu Qian
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Jacques Briand
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Cynthia M. Rominger
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Catherine Oleykowski
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Mary Ann Hardwicke
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
| | - Juan I. Luengo
- Cancer Metabolism Chemistry; ‡Cancer Metabolism Biology; and §Platform Technology & Sciences, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426-0989, United States
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36
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Scholes DT, Hawks SA, Yee PY, Wu H, Lindemuth JR, Tolbert SH, Schwartz BJ. Overcoming Film Quality Issues for Conjugated Polymers Doped with F4TCNQ by Solution Sequential Processing: Hall Effect, Structural, and Optical Measurements. J Phys Chem Lett 2015; 6:4786-4793. [PMID: 26554820 DOI: 10.1021/acs.jpclett.5b02332] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate that solution-sequential processing (SqP) can yield heavily doped pristine-quality films when used to infiltrate the molecular dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) into pure poly(3-hexylthiophene) (P3HT) polymer layers. Profilometry measurements show that the SqP method produces doped films with essentially the same surface roughness as pristine films, and 2-D grazing-incidence wide-angle X-ray scattering (GIWAXS) confirms that SqP preserves both the size and orientation of the pristine polymer's crystallites. Unlike traditional blend-cast F4TCNQ/P3HT doped films, our sequentially processed layers have tunable and reproducible conductivities reaching as high as 5.5 S/cm even when measured over macroscopic (>1 cm) distances. The high conductivity and superb film quality allow for meaningful Hall effect measurements, which reveal p-type conduction and carrier concentrations tunable from 10(16) to 10(20) cm(-3) and hole mobilities ranging from ∼0.003 to 0.02 cm(2) V(-1) s(-1) at room temperature over the doping levels examined.
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Affiliation(s)
| | | | | | | | | | - Sarah H Tolbert
- California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States
| | - Benjamin J Schwartz
- California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States
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Zhang G, Hawks SA, Ngo C, Schelhas LT, Scholes DT, Kang H, Aguirre JC, Tolbert SH, Schwartz BJ. Extensive Penetration of Evaporated Electrode Metals into Fullerene Films: Intercalated Metal Nanostructures and Influence on Device Architecture. ACS Appl Mater Interfaces 2015; 7:25247-25258. [PMID: 26488157 DOI: 10.1021/acsami.5b06944] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Although it is known that evaporated metals can penetrate into films of various organic molecules that are a few nanometers thick, there has been little work aimed at exploring the interaction of the common electrode metals used in devices with fullerene derivatives, such as organic photovoltaics (OPVs) or perovskite solar cells that use fullerenes as electron transport layers. In this paper, we show that when commonly used electrode metals (e.g., Au, Ag, Al, Ca, etc.) are evaporated onto films of fullerene derivatives (such as [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)), the metal penetrates many tens of nanometers into the fullerene layer. This penetration decreases the effective electrical thickness of fullerene-based sandwich structure devices, as measured by the device's geometric capacitance, and thus significantly alters the device physics. For the case of Au/PCBM, the metal penetrates a remarkable 70 nm into the fullerene, and we see penetration of similar magnitude in a wide variety of fullerene derivative/evaporated metal combinations. Moreover, using transmission electron microscopy to observed cross-sections of the films, we show that when gold is evaporated onto poly(3-hexylthiophene) (P3HT)/PCBM sequentially processed OPV quasi-bilayers, Au nanoparticles with diameters of ∼3-20 nm are formed and are dispersed entirely throughout the fullerene-rich overlayer. The plasmonic absorption and scattering from these nanoparticles are readily evident in the optical transmission spectrum, demonstrating that the interpenetrated metal significantly alters the optical properties of fullerene-rich active layers. This opens a number of possibilities in terms of contact engineering and light management so that metal penetration in devices that use fullerene derivatives could be used to advantage, making it critical that researchers are aware of the electronic and optical consequences of exposing fullerene-derivative films to evaporated electrode metals.
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Affiliation(s)
- Guangye Zhang
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - Steven A Hawks
- Department of Materials Science and Engineering, University of California, Los Angeles , Los Angeles, California 90095, United States
| | - Chilan Ngo
- Department of Materials Science and Engineering, University of California, Los Angeles , Los Angeles, California 90095, United States
| | - Laura T Schelhas
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - D Tyler Scholes
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - Hyeyeon Kang
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - Jordan C Aguirre
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
- Department of Materials Science and Engineering, University of California, Los Angeles , Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
- California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States
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Huber RC, Ferreira AS, Thompson R, Kilbride D, Knutson NS, Devi LS, Toso DB, Challa JR, Zhou ZH, Rubin Y, Schwartz BJ, Tolbert SH. POLARON DYNAMICS. Long-lived photoinduced polaron formation in conjugated polyelectrolyte-fullerene assemblies. Science 2015; 348:1340-3. [PMID: 26089510 PMCID: PMC6039100 DOI: 10.1126/science.aaa6850] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid movement of charge carriers out of a critical recombination range. If synthetic organic photovoltaic materials could mimic this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous solution.
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Affiliation(s)
- Rachel C Huber
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Amy S Ferreira
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Robert Thompson
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Daniel Kilbride
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Nicholas S Knutson
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Lekshmi Sudha Devi
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Daniel B Toso
- Department of Microbiology, Immunology and Molecular Genetics, and the Biomedical Engineering Program, UCLA, Los Angeles, CA 90095, USA
| | - J Reddy Challa
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, and the Biomedical Engineering Program, UCLA, Los Angeles, CA 90095, USA. The California NanoSystems Institute (CNSI), UCLA, Los Angeles, CA 90095, USA
| | - Yves Rubin
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA. The California NanoSystems Institute (CNSI), UCLA, Los Angeles, CA 90095, USA.
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California-Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA. The California NanoSystems Institute (CNSI), UCLA, Los Angeles, CA 90095, USA. Department of Materials Science and Engineering, UCLA, Los Angeles, CA 90095, USA.
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Glover WJ, Casey JR, Schwartz BJ. Free Energies of Quantum Particles: The Coupled-Perturbed Quantum Umbrella Sampling Method. J Chem Theory Comput 2014; 10:4661-71. [DOI: 10.1021/ct500661t] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- William J. Glover
- Department of Chemistry and
Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Jennifer R. Casey
- Department of Chemistry and
Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J. Schwartz
- Department of Chemistry and
Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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40
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Guardado-Alvarez TM, Devi LS, Vabre JM, Pecorelli T, Schwartz BJ, Durand JO, Mongin O, Blanchard-Desce M, Zink JI. Photo-redox activated drug delivery systems operating under two photon excitation in the near-IR. Nanoscale 2014; 6:4652-8. [PMID: 24647752 PMCID: PMC4305343 DOI: 10.1039/c3nr06155h] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We report the design and synthesis of a nano-container consisting of mesoporous silica nanoparticles with the pore openings covered by "snap-top" caps that are opened by near-IR light. A photo transducer molecule that is a reducing agent in an excited electronic state is covalently attached to the system. Near IR two-photon excitation causes inter-molecular electron transfer that reduces a disulfide bond holding the cap in place, thus allowing the cargo molecules to escape. We describe the operation of the "snap-top" release mechanism by both one- and two-photon activation. This system presents a proof of concept of a near-IR photoredox-induced nanoparticle delivery system that may lead to a new type of photodynamic drug release therapy.
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Affiliation(s)
- Tania M. Guardado-Alvarez
- Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, California 90095-1569
| | - Lekshmi Sudha Devi
- Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, California 90095-1569
| | - Jean-Marie Vabre
- Chimie et Photonique Moléculaires, CNRS UMR 6510, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex (France)
| | - Travis Pecorelli
- Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, California 90095-1569
| | - Benjamin J. Schwartz
- Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, California 90095-1569
| | - Jean-Olivier Durand
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1, CC1701 Place Eugène Bataillon, 34095 Montpellier Cedex 05, France
| | - Olivier Mongin
- Chimie et Photonique Moléculaires, CNRS UMR 6510, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex (France)
- Institut des Sciences Chimiques de Rennes, CNRS UMR 6226, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
| | - Mireille Blanchard-Desce
- Chimie et Photonique Moléculaires, CNRS UMR 6510, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex (France)
- Univ. Bordeaux, Institut des Sciences Moléculaires, CNRS UMR 5255, 351 Cours de la Libération, F-33405 Talence Cedex, France
| | - Jeffrey I. Zink
- Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, California 90095-1569
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41
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Van Aller GS, Pappalardi MB, Ott HM, Diaz E, Brandt M, Schwartz BJ, Miller WH, Dhanak D, McCabe MT, Verma SK, Creasy CL, Tummino PJ, Kruger RG. Long residence time inhibition of EZH2 in activated polycomb repressive complex 2. ACS Chem Biol 2014; 9:622-9. [PMID: 24304166 DOI: 10.1021/cb4008748] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
EZH2/PRC2 catalyzes transcriptionally repressive methylation at lysine 27 of histone H3 and has been associated with numerous cancer types. Point mutations in EZH2 at Tyr641 and Ala677 identified in non-Hodgkin lymphomas alter substrate specificity and result in increased trimethylation at histone H3K27. Interestingly, EZH2/PRC2 is activated by binding H3K27me3 marks on histones, and this activation is proposed as a mechanism for self-propagation of gene silencing. Recent work has identified GSK126 as a potent, selective, SAM-competitive inhibitor of EZH2 capable of globally decreasing H3K27 trimethylation in cells. Here we show that activation of PRC2 by an H3 peptide trimethylated at K27 is primarily an effect on the rate-limiting step (kcat) with no effect on substrate binding (Km). Additionally, GSK126 is shown to have a significantly longer residence time of inhibition on the activated form of EZH2/PRC2 as compared to unactivated EZH2/PRC2. Overall inhibition constant (Ki*) values for GSK126 were determined to be as low as 93 pM and appear to be driven by slow dissociation of inhibitor from the activated enzyme. The data suggest that activation of EZH2 allows the enzyme to adopt a conformation that possesses greater affinity for GSK126. The long residence time of GSK126 may be beneficial in vivo and may result in durable target inhibition after drug systemic clearance.
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Affiliation(s)
- Glenn S. Van Aller
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Melissa Baker Pappalardi
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Heidi M. Ott
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Elsie Diaz
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Martin Brandt
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Benjamin J. Schwartz
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - William H. Miller
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Dashyant Dhanak
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Michael T. McCabe
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Sharad K. Verma
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Caretha L. Creasy
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Peter J. Tummino
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Ryan G. Kruger
- Cancer Epigenetics Discovery Performance Unit, Cancer Research, Oncology R&D and ‡Platform Technology and Sciences, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, Pennsylvania 19426, United States
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Guardado-Alvarez TM, Sudha Devi L, Russell MM, Schwartz BJ, Zink JI. Correction to “Activation of Snap-Top Capped Mesoporous Silica Nanocontainers Using Two Near-Infrared Photons”. J Am Chem Soc 2013. [DOI: 10.1021/ja410105b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
The hydrated electron-the species that results from the addition of a single excess electron to liquid water-has been the focus of much interest both because of its role in radiation chemistry and other chemical reactions, and because it provides for a deceptively simple system that can serve as a means to confront the predictions of quantum molecular dynamics simulations with experiment. Despite all this interest, there is still considerable debate over the molecular structure of the hydrated electron: does it occupy a cavity, have a significant number of interior water molecules, or have a structure somewhere in between? The reason for all this debate is that different computer simulations have produced each of these different structures, yet the predicted properties for these different structures are still in reasonable agreement with experiment. In this Feature Article, we explore the reasons underlying why different structures are produced when different pseudopotentials are used in quantum simulations of the hydrated electron. We also show that essentially all the different models for the hydrated electron, including those from fully ab initio calculations, have relatively little direct overlap of the electron's wave function with the nearby water molecules. Thus, a non-cavity hydrated electron is better thought of as an "inverse plum pudding" model, with interior waters that locally expel the surrounding electron's charge density. Finally, we also explore the agreement between different hydrated electron models and certain key experiments, such as resonance Raman spectroscopy and the temperature dependence and degree of homogeneous broadening of the optical absorption spectrum, in order to distinguish between the different simulated structures. Taken together, we conclude that the hydrated electron likely has a significant number of interior water molecules.
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Affiliation(s)
- Jennifer R Casey
- Department of Chemistry and Biochemistry, University of California, Los Angeles , Los Angeles, California 90095-1569, United States
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44
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Kahros A, Schwartz BJ. Response to "Comment on 'Going beyond the frozen core approximation: development of coordinate-dependent pseudopotentials and application to Na2(+)'" [J. Chem. Phys. 139, 147101 (2013)]. J Chem Phys 2013; 139:147102. [PMID: 24116653 DOI: 10.1063/1.4823833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Stoll, Fuentealba, and Szentpály (SFS) argue that the coordinate-dependent pseudopotential we developed for the sodium dimer cation molecule is inferior to other potentials that have been presented in the literature for this molecule. The goal of our work, however, was to present a novel method for the development of rigorous coordinate-dependent pseudopotentials. Our method is designed to reproduce all-electron Hartree-Fock calculations without the inclusion of adjustable parameters. Moreover, our method starts from the superposition of unoptimized, non-norm-conserved atomic potentials, so that when complete, the resulting norm-conserving potential can reproduce an all-electron Hartree-Fock calculation without the inclusion of adjustable parameters. We chose the sodium dimer cation system as a proof of principle for our method, and showed that our method does indeed allow a one-electron calculation to correctly reproduce the all-electron Hartree-Fock calculation from bonding to the dissociation limit. Our purpose in developing this method is to use such potentials in condensed-phase mixed quantum/classical molecular dynamics simulations, where inclusion of valence polarization effects is unimportant or can be added on after the fact. Thus we do not claim that our method provides a potential that is superior to potentials that have been specifically constructed to go beyond the static exchange approximation and/or include valence polarization effects-such potentials are beyond the scope of our work. We also note that although we made a numerical error in the application of our method to Na2(+) in our original work [A. Kahros and B. J. Schwartz, J. Chem. Phys. 138, 054110 (2013)] that led to an overestimation of the magnitude of core polarization effects for this particular molecule, out method does work as derived for this molecule and the error does not affect the significance of our method or its general applicability.
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Affiliation(s)
- Argyris Kahros
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, USA
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45
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Kahros A, Schwartz BJ. Erratum: “Going beyond the frozen core approximation: Development of coordinate-dependent pseudopotentials and application to Na 2+” [J. Chem. Phys. 138, 054110 (2013)]. J Chem Phys 2013. [DOI: 10.1063/1.4823770] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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46
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Guardado-Alvarez TM, Sudha Devi L, Russell MM, Schwartz BJ, Zink JI. Activation of snap-top capped mesoporous silica nanocontainers using two near-infrared photons. J Am Chem Soc 2013; 135:14000-3. [PMID: 24015927 PMCID: PMC3862188 DOI: 10.1021/ja407331n] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Photoactivation of "snap-top" stoppers over the pore openings of mesoporous silica nanoparticles releases intact cargo molecules from the pores. The on-command release can be stimulated by either one UV photon or two coherent near-IR photons. Two-photon activation is particularly desirable for use in biological systems because it enables good tissue penetration and precise spatial control. Stoppers were assembled by first binding photolabile coumarin-based molecules to the nanoparticle surface. Then, after the particles were loaded with cargo, bulky β-cyclodextrin (CD) molecules were noncovalently associated with the substituted coumarin molecule, blocking the pores and preventing the cargo from escaping. One-photon excitation at 376 nm or two-photon excitation at 800 nm cleaves the bond holding the coumarin to the nanopore, releasing both the CD cap and the cargo. The dynamics of both the cleavage of the cap and the cargo release was monitored using fluorescence spectroscopy. This system traps intact cargo molecules without the necessity of chemical modification, releases them with tissue-penetrating near-IR light, and has possible applications in photostimulated drug delivery.
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Affiliation(s)
- Tania M Guardado-Alvarez
- Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California , Los Angeles, California 90095-1569, United States
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47
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Doan SC, Schwartz BJ. Nature of Excess Electrons in Polar Fluids: Anion-Solvated Electron Equilibrium and Polarized Hole-Burning in Liquid Acetonitrile. J Phys Chem Lett 2013; 4:1471-1476. [PMID: 26282301 DOI: 10.1021/jz400621m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Stephanie C Doan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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48
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Clark APZ, Shi C, Ng BC, Wilking JN, Ayzner AL, Stieg AZ, Schwartz BJ, Mason TG, Rubin Y, Tolbert SH. Self-assembling semiconducting polymers--rods and gels from electronic materials. ACS Nano 2013; 7:962-977. [PMID: 23346927 DOI: 10.1021/nn304437k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.
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Affiliation(s)
- Andrew P-Z Clark
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095, USA
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49
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Kahros A, Schwartz BJ. Going beyond the frozen core approximation: Development of coordinate-dependent pseudopotentials and application to Na 2+. J Chem Phys 2013; 138:054110. [DOI: 10.1063/1.4789425] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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50
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Ayzner AL, Doan SC, Tremolet de Villers B, Schwartz BJ. Ultrafast Studies of Exciton Migration and Polaron Formation in Sequentially Solution-Processed Conjugated Polymer/Fullerene Quasi-Bilayer Photovoltaics. J Phys Chem Lett 2012; 3:2281-2287. [PMID: 26295784 DOI: 10.1021/jz300762c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We examine the ultrafast dynamics of exciton migration and polaron production in sequentially processed 'quasi-bilayer' and preblended 'bulk heterojunction' (BHJ) solar cells based on conjugated polymer films that contain the same total amount of fullerene. We find that even though the polaron yields are similar, the dynamics of polaron production are significantly slower in quasi-bilayers than BHJs. We argue that the different polaron production dynamics result from the fact that (1) there is significantly less fullerene inside the polymer in quasi-bilayers than in BHJs and (2) sequential processing yields polymer layers that are significantly more ordered than BHJs. We also argue that thermal annealing improves the performance of quasi-bilayer solar cells not because annealing drives additional fullerene into the polymer but because annealing improves the fullerene crystallinity. All of the results suggest that sequential processing remains a viable alternative for producing polymer/fullerene solar cells with a nanometer-scale architecture that differs from BHJs.
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Affiliation(s)
- Alexander L Ayzner
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | - Stephanie C Doan
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
| | | | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, United States
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